A storage device (such as NAND flash memory) may be powered off at any time. If the NAND flash memory is powered off during erasing, the erasing block may not be programmed directly even if this block looks like a good block. If the NAND flash memory is powered off during programming, the programming page may not be programmed again even if this page looks like non-program page. If the NAND flash memory is MLC (Multi-Level-Cell 2 bit/cell) and the programming page is a lower page (group A), its upper page (group B) may also cause new data crash. If the NAND flash memory is TLC (3 bit/cell) and the programming page is a lower page (group A or group B), its upper page (group B and group C) may also cause new data crash.